The authors present an analysis of the results of laboratory immunological examination of 52 patients suffering from recurrent respiratory infections. Besides the typical laboratory correlates of chronic inflammation, several findings indicated the depressed function of cellular and partially humoral immunity. The immunological parameters, most frequently decreased in comparison with normal values, were as follows: the response to the recall antigens of Imunoskintest (lower in 54% of patients), the relative number of CD3+ lymphocytes (35%), the CD4/CD8 ratio (37%), phagocytic activity (37%) and also serum IgA (12%). This means that more than two thirds of patients displayed at the time of examination a substantial alteration of one or more immunological parameters, the depression of cellular immunity was much more pronounced. It is concluded that the laboratory immunological examination of patients with recurrent respiratory infections is very important for revealing of an underlying cause of the disease and for indicating the adequate immunomodulatory treatment.